1. Field of the Invention
This invention relates to a novel laked azo pigment, processes for its preparation and to coating, plastic and ink compositions containing the pigment.
2. Description of Related Art
Metal salts of individual azo compounds containing a pyrazolone moiety containing one or two acid groups are known in the art as pigments. Azo yellow pigments are a class of colorants that are tinctorially strong and relatively inexpensive. Monoazo yellow pigments exhibit good lightfastness and are useful as coloring agents for paints and some printing inks. In plastics, however, monoazo yellow pigments tend to undesirably bloom and discolor at high temperatures, so their use is disfavored.
For example, German Patent 2,616,981 describes metal salts of pyrazolone azo dyes which are obtained by coupling diazotized 2-amino-4, 5-dichlorobenzene-l-sulfonic acid with 1-(sulfoaryl)-3-methyl-5-pyrazolone compounds and subsequent laking with metal salts.
Japanese Patent 62,166,359 describes electrophotographic toners that contain monoazo pigments of the formula ##STR2##
X=Cl or SO.sub.3.sup.- ; m=1 or 2; M=Mg, Ca or Ba; n=1 or 2. When X is Cl, then m is 1 and n is 2, and when X is SO.sub.3.sup.-, then m is 2 and n is 1.
U.S. Pat. No. 4,594,411 describes ##STR3##
wherein R is CH.sub.3 or COO.sup.- ; X is Cl, CH.sub.3, CH.sub.3 O, C.sub.2 H.sub.5 O C.sub.2 H.sub.5 CONH, NH.sub.2 CONH, C.sub.6 H.sub.5 CONH, CH.sub.3 SO.sub.2 NH, CH.sub.3 CONH, or hydrogen; Y is hydrogen, Cl, or CH3; Z is hydrogen or Cl, n is 0, 1 or 2; Me.sup.+ is one equivalent of a cation selected from the group consisting of NH.sub.4.sup.+, Li.sup.+, K.sup.+, Na.sup.+, 1/2 Sr.sup.2+, 1/2 Mn.sup.2+, 1/2 Ni.sup.2+, 1/2 Ba.sup.2+, 1/2 Mg.sup.2+ and 1/2 Ca.sup.2+ ; with the provision that if R is COO.sup.-, the additional equivalent charge is compensated by a further equivalent of said or another cation. ##STR4##
wherein D is tri or tetrasubstituted phenyl ring; R is CH.sub.3 or COO.sup.- ; X is Cl, Br, CH.sub.3, CH.sub.3 O, C.sub.2 H.sub.5 O CH.sub.3 CONH, SO.sub.2 NH.sub.2, SO.sub.3.sup.- ; Y is Cl, Br, CH.sub.3 or SO.sub.3.sup.- ; Z is Cl, Br or CH.sub.3.
U.S. Pat. No. 5,047,517 relates to a yellow monoazo pigment which is obtained by diazotization of 2-amino-4-chloro-5-methylbenzene-1-sulfonic acid, coupling of the diazonium compound with 1-(3'-sulfophenyl)-3-methyl-5-pyrazolone and subsequent laking of the coupling product to the calcium salt.
U.S. Pat. No. 5,669,967 relates to a yellow monoazo pigment which is obtained by diazotization of 2-amino-5-chloro-4-methylbenzene-1-sulfonic acid, coupling of the diazonium compound with 1-(2'-chlorophenyl)-3-methyl-5-pyrazolone and subsequent laking of the coupling product to a divalent metal salt.
There is a desire, however, to obtain migration resistant yellow pigments with high heat stability and ease of preparation as well as reduced cost. There is also a need for these yellow pigments to show improved performance in one or more of the following properties: color strength, resistance to polar solvents and lightfastness.